The invention concerns a process for manufacturing and/or treating an endless tubular felt or similar tubular structure. A material, for instance, a fiber web, a coating, longitudinal threads or the like, are deposited continuously across the width. An at least partially prepared tubular felt revolves circumferentially with the deposition being in that direction. The tubular felt may be treated across a width which has been singed or needled and with the width being less than the width of the tubular felt. The deposition or the treatment takes place, respectively, by a relative motion of, or toward, the tubular felt in a helical manner transversely to its direction of advance and possibly with partial overlap. The invention further relates to an apparatus to implement this process and comprises at least two mutually spaced conveyor rollers for the already-prepared part of the tubular felt. A feed system for depositing the material on the already-prepared part of the tubular felt and/or with a treatment system for said part is disclosed. A displacement device for the relative motion between the tubular felt and the feed system or the treatment system is provided in the axial direction of the conveyor rollers.
Such a process and pertinent equipment is disclosed in the German Pat. No. 16 60 765. To that end, the equipment includes two mutually adjustable conveyor rollers on which the already-prepared part of the tubular felt moves. A fiber-web is continuously supplied in the direction of rotation of the tubular felt in such a manner that this length of fiber web partly overlaps the already-prepared tubular felt by one edge. After the fiber web is deposited, it is needled to the tubular felt. Grooves are fashioned into the conveyor rollers parallel to their longitudinal axes and are adapted to receive moving conveyor chains which support needles for penetrating the felt. These conveyor chains slowly displace the tubular felt transversely to its direction of advance, whereby the tubular felt is gradually built-up over its entire width. It has been found in practice that the transverse motion of the tubular felt does not coincide with the motion of the conveyor chains. This was noted when the computed tube width was not obtained after a computed number of tube revolutions. The reasons for this discrepancy have not been reliably ascertained. As a consequence, the specific weight per area and hence the thickness of the particular tubular felt varies greatly and, consequently, the dehydration properties and also the service life of the tubular felt are degraded when used in a paper-making machine.
The equipment disclosed in the German Auslegeschrift No. 23 24 985 operates in the kinematic reverse order. In this equipment, the tubular felt is not displaced transversely but rather the feed system for the fiber web is. However, the tubular felt is similarly formed by the length of fiber web being opposed helically with partial overlap.
In this instance, too, the lengths of fiber web must be so deposited that there will be no changes in specific weight per area or thickness. These changes may be caused, for instance, by an uncontrolled drift of the tube on the conveyor rollers or by fluctuations in the transverse motion of the feed system.
Similar problems are incurred if in lieu of a length of fiber web, coatings or chemicals are deposited in helical manner. Again, the spacings of the "pitches" on the tubular felt must always be of a predetermined value in order to have uniform deposition.
Similar considerations apply to treatments and procedures such as singeing, needling, brushing or the like. One may move a corresponding device of lesser width across the width of the circumferentially rotating tubular felt or, vice-versa, the tubular felt can be moved transversely underneath the stationary device. Similar kinematic relations apply when treating tubular felts or corresponding tubular structures in roll calenders.
Lastly, threads forming longitudinal dehydration channels which are mutually spaced apart can also be deposited to form a tubular felt by placing one or more threads next to each other in the gaps of a reed on the surface of the tubular felt. By transversely moving either the tubular felt or the feed system for the threads, these threads may be arrayed helically on the tubular felt. Uniformly spaced filaments are also essential in this instance.